Amblyopia is decreased visual acuity (usually greater in one eye) for which no organic cause can be detected by physical examination of the eye. The prevalence of amblyopia in the U.S. is 5%. Yet, as many as 72% of amblyopes go undetected and untreated. If intervention is to be maximally effective, action must be taken early in the disease process, prior to the end of critical periods in the developing human visual system. Unfortunately visual acuity screening programs come too late and have not been effective in the early identification of amblyopes. The goal of this pilot project is to develop and refine a random-dot stereoacuity test (RDS) that may be a highly-sensitive test for the early identification of infants who are at risk of developing vision loss due to amblyopia. The premise in support of this goal is the prior finding that binocular RDS performance is more sensitive to the effects of uniocular blur than is either monocular or binocular Snellen visual acuity. Initial studies concentrate on the refinement of methods in older subjects that will eventually be applied to testing in high-risk infants.